Sound systems are commonly found in homes, offices and vehicles for generating audio output. In an automobile, for instance, the sound system may include a head unit such as a radio, tape player, compact disc player, or mp3 player. The head unit in some vehicles may even include a DVD player with a liquid crystal display screen mounted into the center dash console, interior roof, or headrest backs. The head unit in some vehicles may also include an automotive navigation system for directing the driver to his or her destination.
The head unit functions so as to direct an electrical signal of a particular frequency to a speaker to produce a desired sound. A speaker generally includes a voice coil attached to an apex of a cone. The voice coil is oriented inside of a gap established between a permanent magnet. Application of the electrical signal to the voice coil causes an electromagnet to be formed. The voice coil and cone then vibrate to produce sound at the frequency of the electrical signal. Speakers run off of A/C current while other components of the sound system and vehicle generally run off of D/C current.
As the vast majority of sound systems in automobiles deliver stereo sound, multiple speakers are located in the interior driving compartment. Stereo sound seeks to mimic natural sound by generating sound from two or more directions. In this regard, two or more independent audio channels may be used to create sounds through symmetrically configured speakers. Speakers in automobiles may be located in the dashboard, doors, or back window area. Various types of speakers include tweeters for use with small, high frequencies, and woofers for large, low frequencies. Midrange speakers are also available for handling frequencies between small and large. Additional types of speakers that may be incorporated into vehicle sound systems include subwoofers that are used in conjunction with bass frequencies.
Sound systems in vehicles can thus be provided that are more powerful and offer different features than those included standard in the vehicle by the manufacturer. Typically, an upgraded alternator and/or an additional battery are installed into the vehicle in order to provide the necessary additional power. Additional power may also be desirable should one wish to keep the sound system running when the engine is turned off. For example, tailgating at football games is a common activity in which it is desirable to run the sound system of a vehicle while the engine is shut off. While additional power may be desirable, it is to be understood that upgraded alternators and/or additional batteries are not always used or needed when running a sound system during tailgating. Further, since the tailgaters are generally located outside of the vehicle, a sound system with speakers in the interior compartment may not be adequate as the generated sound may be muffled. As such, additional speakers located closer to the tailgaters, possibly outside of the interior compartment, may be included in order to cause a higher quality sound to be heard. Unfortunately, the incorporation of speakers in addition to those in the interior compartment requires additional controlling elements be included in order to effect their operation. As such, there remains room for variation and improvement within the art.